Method of folding an airbag for a vehicle safety restraint

ABSTRACT

An airbag (1) for a vehicle safety restraint and particularly a method of folding an airbag comprising laying the airbag (1) generally flat, making folds in the flat airbag to form a polygon (such as a square) in plan view, folding all of the sides of the polygon upwardly and inwardly of the polygon considered in plan view so that at least one point on each side meets a point on at least one other side at a position generally above the centre of the polygon so that the corners of the polygon form upstanding ears (7), and subsequently rolling (E) the upstanding corner ears of the polygon to form the airbag into a cylindrical shape. An airbag folded in this way is very compact and will fit into a housing of smaller diameter than was hitherto possible. The invention applies particularly to a driver&#39;s side airbag.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to an airbag for a vehicle safetyrestraint and particularly to a method of folding a uninflated airbagfor storage in the vehicle. The method applies primarily to a driver'sside airbag but can easily be adapted to a passenger side bag, to a sideimpact bag or to other forms of airbag.

Airbags are relatively bulky accessories and there is a desire tominimise the space occupied by the folded bag in the vehicle. This isparticularly true of a driver's side airbag which is usually housed inthe hub of a steering wheel and thus must fit into a very small space,particularly in the smaller steering wheels used in sport model vehiclesor other customised designs. Traditionally an uninflated airbag isfolded in consecutive overlapping folds until it occupies the requisitespace. Often pressure and sometimes heat is applied to compact itfurther.

The present invention aims to provide a method by which an airbag can befolded into a smaller diameter housing giving a more compact module thanis possible with traditional methods.

According to the present invention there is provided a method of foldingan airbag comprising laying the airbag generally flat, making folds inthe flat airbag to form a polygon in plan view, folding all of the sidesof the polygon upwardly and inwardly of the polygon considered in planview so that at least one point on each side meets a point on at leastone other side at a position generally above the centre of the polygonso that the corners of the polygon form upstanding ears, andsubsequently rolling the upstanding corner ears of the polygon to formthe airbag into a cylindrical shape.

According to a preferred embodiment of symmetry or relative to lines ofsymmetry of the first formed polygon, for example lying at 45° and lessto respectively the first and second lines a method is provided offolding an airbag wherein the step of making folds in the flat airbagcomprises the airbag folding subsequently folding the airbag alongparallel lines spaced equidistantly on opposite sides of a line ofsymmetry, perpendicular to the first line of symmetry. These foldingsteps may be repeated to form a smaller polygon. The further folding maybe relative to the same lines of symmetry or relative to lines ofsymmetry of the first formed polygon, for example lying at 45° and lessto respectively the first and second lines.

According to a preferred embodiment a method is provided wherein thecorner turning or bending step is accompanied or preceded by a step ofstretching the corner ears in a radially outward direction, and/or offlattening the corner ears by applying force at opposite sides of eachear, particularly at those parts of the corner ears which bulge or archoutwardly.

For a better understanding of the present invention and to show how thesame may be carried into effect, reference will now be made to theaccompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 9 comprise a sequence of steps of a method of folding anairbag according to the invention;

FIG. 10 illustrates a side view of the airbag as folded in FIG. 8;

FIG. 11 is a side view of the airbag as folded in FIG. 9; and

FIG. 12 is a side view of the fully folded airbag according to themethod of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In each Figure an airbag 1 is shown schematically in plan view. Theairbag 1 is a driver's side airbag and is circular in plan view in theuninflated state.

The airbag 1 comprises two circles of airbag fabric which are stitchedor welded together around their periphery to form a hollow cushion. Agap may be left in the stitching for the inflation inlet, oralternatively a hole is more usually formed toward the centre of one ofthe circular fabric pieces.

The first folding step is shown in FIG. 1 and comprises folding the bag1 along lines A so that opposing outer edges are brought together at thecentre line AA. This is indicated by arrows 2 and 3 respectively, andforms the oblong shape shown in FIG. 2. The edges may overlap or beseparated by a gap, or abut each other at the line AA. The exactarrangement depends upon the diameter-height ratio of the housing intowhich the airbag is to be fitted. For example for a shallow housing oflarge diameter the edges should preferably overlap whereas for a deephousing of smaller diameter they should be separated so that there isonly one layer of fabric at the centre.

The shape thus formed is folded again as indicated in FIG. 3 along eachof lines B. Lines B are perpendicular to lines A and are equispacedabout centre line BB. This forms a regular polygon in the form of asquare as shown in FIG. 4.

The corners of the square thus formed are folded in again this timealong lines C, as indicated in FIG. 5 to form a smaller square as shownin FIG. 6.

The sides of the folded airbag are then brought to and towards eachother at the centre of the square. This is shown by the arrows D in FIG.7. The centres of the sides of the square all come together generallyabove the centre of the square as shown in FIG. 8. This causes thecorners to stick out more prominently and form upstanding ears 7 asshown in FIG. 8 and in side view in FIG. 10. These corner ears 7 arethen pulled radially outward in directions F (FIG. 9) and bent over orturned circumferentially in the direction of arrows E in FIG. 9 and FIG.11 so that the ears 7 are flattened against the sides of the polygon.The ears are then each rolled and if necessary the upper corner istucked in to form the particularly compact folded shape for the airbagillustrated in FIG. 12.

An improvement is further produced if pressure is applied to the lobesof the protruding corner ears 7, as indicated by arrows G in FIG. 9.This flattens the corner ears and further compacts the folded airbag.This step could replace or compliment the corner stretching step (F,FIG. 9).

What is claimed is:
 1. A method of folding an airbag for insertion in anairbag housing in a vehicle comprising the steps of:laying the airbaggenerally flat; making folds in the flat airbag to form a polygon inplan view, the polygon having a geometric centre, a plurality of cornersand a plurality of sides, the plurality of corners being equal to theplurality of sides, the method further comprising:folding each of theplurality of sides of the polygon upwardly and inwardly of the polygonconsidered in plan view so at least one point on each of the pluralityof sides meets a point on at least one other of the plurality of sidesat a position generally above the centre of the polygon so that each ofthe plurality of corners of the polygon form a respective upstandingcorner ear, and subsequently:rolling the upstanding corner ears of thepolygon to flatten them against the sides of the polygon and to form theairbag into a cylindrical shape.
 2. A method according to claim 1wherein the polygon is a regular polygon.
 3. A method according to claim2 wherein the polygon is a square.
 4. A method of folding an airbagaccording to claim 1, wherein the step of making folds in the flatairbag comprises folding the airbag along parallel lines spacedequidistantly on opposite sides of a first line of symmetry of theairbag and subsequently folding the airbag along parallel lines spacedequidistantly on opposite sides of a second line of symmetry of theairbag, the second line being perpendicular to the first line ofsymmetry.
 5. A method according to claim 4 wherein the first and secondlines of symmetry are centre lines of the flat airbag in plan view.
 6. Amethod according to claim 5, wherein the step of making folds isrepeated.
 7. A method according to claim 1, wherein the corner turningstep is accompanied or preceded by a step of stretching the corner earsin a radially outward direction, and/or of flattening the corner ears byapplying force at opposite sides of each ear.
 8. A method of folding anairbag housing in a vehicle comprising the steps of:laying the airbaggenerally flat; making folds in the flat airbag to form a polygon inplan view, the polygon having a geometric centre, a plurality of cornersand a plurality of sides, the method further comprising:folding eachside of the polygon upwardly and inwardly of the polygon considered inplan view so that at least one point on each side meets a point on atleast one other side at a position generally above the centre of thepolygon so that each corner of the polygon forms a respective upstandingcorner ear, rolling each upstanding corner ear to flatten them againstthe sides of the polygon and to form the airbag into a cylindricalshape, and stretching the corner ears in a radially outward direction.9. A method according to claim 8 wherein the step of stretching thecorner ears accompanies the step of rolling the corner ears.
 10. Amethod according to claim 8 wherein the step of stretching the cornerears is preceded by the step of rolling the corner ears.
 11. A methodaccording to claim 8 further comprising the step of flattening thecorner ears by applying force at opposite sides of each ear.